US20100263467A1 - Roller screw - Google Patents
Roller screw Download PDFInfo
- Publication number
- US20100263467A1 US20100263467A1 US12/740,924 US74092408A US2010263467A1 US 20100263467 A1 US20100263467 A1 US 20100263467A1 US 74092408 A US74092408 A US 74092408A US 2010263467 A1 US2010263467 A1 US 2010263467A1
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- United States
- Prior art keywords
- path
- roller rolling
- nut
- rollers
- scooping
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
- F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
- F16H25/20—Screw mechanisms
- F16H25/22—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members
- F16H25/2247—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with rollers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16H—GEARING
- F16H25/00—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms
- F16H25/18—Gearings comprising primarily only cams, cam-followers and screw-and-nut mechanisms for conveying or interconverting oscillating or reciprocating motions
- F16H25/20—Screw mechanisms
- F16H25/22—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members
- F16H25/2247—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with rollers
- F16H2025/2271—Screw mechanisms with balls, rollers, or similar members between the co-operating parts; Elements essential to the use of such members with rollers with means for guiding circulating rollers
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T74/00—Machine element or mechanism
- Y10T74/19—Gearing
- Y10T74/19642—Directly cooperating gears
- Y10T74/19698—Spiral
- Y10T74/19702—Screw and nut
- Y10T74/19744—Rolling element engaging thread
- Y10T74/19749—Recirculating rolling elements
- Y10T74/19767—Return path geometry
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T74/00—Machine element or mechanism
- Y10T74/19—Gearing
- Y10T74/19642—Directly cooperating gears
- Y10T74/19698—Spiral
- Y10T74/19702—Screw and nut
- Y10T74/19744—Rolling element engaging thread
- Y10T74/19749—Recirculating rolling elements
- Y10T74/19767—Return path geometry
- Y10T74/19772—Rolling element deflector
Definitions
- the present invention relates to a roller screw having rollers movably interposed between a screw shaft and a nut.
- roller screw having rollers movably interposed between a screw shaft and a nut.
- the roller screw has the advantage of larger load to bear as compared with a ball screw.
- a ball can roll in every direction, the roller can move only in one direction and therefore, there is a problem that the roller is very difficult to circulate.
- the roller screw has a circulation path having a spiral loaded roller rolling path between a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft and a spiral loaded roller rolling surface formed on an inner peripheral surface of the nut and an unloaded return path connecting one end of the loaded roller rolling path to the other end.
- the unloaded return path is formed in a circulation member which is mounted on the nut.
- a lip portion for scooping rollers moving on the roller rolling surface of the screw shaft is provided as a scooping portion for scooping the roller rolling on the spiral loaded roller rolling path. The lip portion juts from the nut toward the roller rolling surface of the screw shaft.
- the inner wall surface of the lip portion of the circulation member is formed tapered with the width that gradually becomes narrower from the unloaded return path toward the loaded roller rolling path (see patent document 1). Then, the rollers moving in the unloaded return path are first aligned to be guided to the loaded roller rolling path.
- the rollers moving in the spiral loaded roller rolling path are scooped by the scooping portion of the circulation member and guided into the unloaded return path.
- the unloaded return path where the scooping portion is formed is arranged in the tangential direction of the loaded roller rolling path (see patent document 2). That is, it is arranged in the tangential direction of the circular loaded roller rolling path seen in the axial direction of the nut and in the lead angle direction of the loaded roller rolling path seen in the side surface direction of the nut.
- Patent document 1 Japanese Patent Application Laid-Open No. 2006-118649
- Patent document 2 Japanese Patent Application Laid-Open No. 11-210858
- rollers move from the loaded roller rolling path to the unloaded return path. If the rollers are scooped up by the lip portion with the narrowed entry, sometimes the rollers may fall to the roller rolling surface side of the screw shaft, come into collision with the edge of the lip portion and cannot be scooped up well. If the rollers come into collision with the edge of the lip portion, the edge of the lip portion may be broken or the rollers may be jammed.
- the end of the side surface of each of the rollers 134 in the axial direction may come into collision with the edge of the scooping portion 132 .
- the roller 134 moving from the loaded roller rolling path to the unloaded return path comes into the scooping portion while it is pushed by the following roller 134 .
- the edge of the scooping portion 132 may be broken or the rollers 134 may be jammed.
- the present invention provides a roller screw capable of preventing rollers moving from an unloaded return path to a loaded roller rolling path from coming into collision with a scooping portion.
- the present invention has another object to provide a roller screw capable of preventing skewing of rollers moving from the unloaded return path to the loaded roller rolling path and enabling smooth movement of the rollers.
- the invention of claim 1 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping portion, provided in the circulation member, for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, the scooping portion having a pair of diagonal corresponding parts that are in contact with diagonal parts of a rectangular side surface of each of the rollers, a width between the diagonal corresponding parts becoming gradually narrower as the diagonal corresponding parts are deeper in the unloaded return
- the invention of claim 2 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping portion, provided in the circulation member, for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, the scooping portion having a pair of diagonal corresponding parts which jut toward the screw shaft from an edge of a continuous path of V shaped cross section connected to the loaded roller rolling surface of the nut and which correspond to diagonal parts of a rectangular side surface of each of the rollers, and a width between the
- the invention of claim 3 is characterized in that in the roller screw of claim 1 or 2 , the roller screw further comprises a plurality of retainers, each provided between adjacent ones of the rollers, for preventing the adjacent rollers from coming into contact with each other, between the diagonal corresponding parts, a lip portion is provided for scooping the retainers out of a circulation raceway into the unloaded return path, and the lip portion has inner wall surfaces that are away from a raceway of the rollers scooped by the diagonal corresponding parts.
- the invention of claim 4 is characterized in that in the roller screw of claim 3 , the inner wall surfaces of the lip portion has a cross section orthogonal to the unloaded return path, which cross section is V shaped in such a manner that an apex angle a formed by connecting the inner wall surfaces of the diagonal corresponding parts and an apex on a diagonal line connecting diagonal parts, out of contact with the diagonal corresponding parts, of each of the rollers scooped by the diagonal corresponding parts is less than 90 degrees.
- the invention of claim 5 is characterized in that in the roller screw of claim 3 or 4 , the inner wall surfaces of the lip portion are formed to be tapered in such a manner that a cross sectional area of the unloaded return path becomes gradually larger from a side of the unloaded return path toward the loaded roller rolling path.
- the invention of claim 6 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping path provided in the unloaded return path and having a scooping portion for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, a moving direction in the scooping path of each of the rollers moving from the loaded roller rolling path to the unloaded return path being outside of a tangential direction of the loaded roller rolling path when seen in an axial direction of the nut.
- the invention of claim 7 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping path provided in the unloaded return path circulation member and having a scooping portion for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, a center line of the scooping path being outside of a tangential direction of the loaded roller rolling path when seen in an axial direction of the nut.
- the invention of claim 8 is characterized in that in the roller screw of claim 6 or 7 , the unloaded return path of the circulation member has a straight path that extends in parallel with an axis line of the nut and direction change paths that are provided at respective ends of the straight path and each have the scooping path, and when seen in the axial direction of the nut, a center line of the scooping path in each of the direction change path is placed outside of a tangential direction of a center line of the loaded roller rolling path and the direction change path is curved at a midpoint toward the straight path so as to connect the scooping path to the straight path.
- the invention of claim 9 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping portion, provided in the circulation member, for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, and the scooping portion covering each of the rollers when a center of the roller is positioned at a boundary between the loaded roller rolling path and the unloaded return path.
- the invention of claim 10 is characterized in that in the roller screw of claim 9 , the unloaded return path has a scooping path where the scooping portion is formed, and a moving direction in the scooping path of each of the rollers moving from the loaded roller rolling path to the unloaded return path is outside of a tangential direction of the loaded roller rolling path when seen in an axial direction of the nut.
- each of the rollers has a spherical end surface.
- the invention of claim 12 is characterized in that in the roller screw of claim 6 , 7 or 9 , the rollers are parallel-arranged with axis lines of adjacent ones of the rollers kept approximately in parallel with each other, the scooping portion having a mountain-shaped lip portion that juts toward the screw shaft and has a first wall part corresponding to an end surface of each of the rollers and a second wall part corresponding to a side surface of the roller, and an edge of the second wall part is closer to the loaded roller rolling path than an edge of the first wall part so that the rollers moving from the loaded roller rolling path to the unloaded return path are constrained by the second wall part before the rollers are constrained by the first wall part.
- the moving direction of the rollers in the scooping path is placed outside the tangential direction of the loaded roller rolling oath, it is possible to make the edge of the scooping portion close to the loaded roller rolling path while keeping enough thickness of the scooping portion.
- the area to constrain the rollers by the scooping portion is longer and the area not to constrain the rollers is shorter, it is possible to prevent skewing of the rollers.
- the moving direction of the rollers in the scooping path is placed outside the tangential direction of the loaded roller rolling oath, it is possible to make the edge of the scooping portion close to the loaded roller rolling path while keeping enough thickness of the scooping portion.
- the area to constrain the rollers by the scooping portion is longer and the area not to constrain the rollers is shorter, it is possible to prevent skewing of the rollers.
- the end part of each roller in the moving direction comes into the scooping portion of the circulation member before the roller gets out of the loaded roller rolling path completely. Therefore, it is possible to eliminate the area not to constrain the roller.
- each roller as the side surface of each roller is first constrained by the lip portion, the end surface of the roller abuts against the edge of the lip portion and the lip portion can be prevented from being damaged.
- FIG. 1 is a perspective view of a roller screw according to an exemplary embodiment of the present invention.
- FIG. 2 is a perspective view of a nut of the above-mentioned roller screw.
- FIG. 3 is a side view illustrating a roller sandwiched between a screw shaft and the nut.
- FIG. 4 is a perspective view of the screw shaft and a circulation member.
- FIG. 5 is a perspective view of a circulation pipe.
- FIG. 6 is a perspective view of a direction change path component.
- FIG. 7 is a perspective view of an R piece.
- FIG. 8 is a perspective view of an end piece.
- FIG. 9 is a perspective view of the nut into which the circulation pipe is inserted.
- FIG. 10 is a perspective view of the nut on which the direction change path component is mounted.
- FIG. 11 is a front view of the nut on which the direction change path component is mounted.
- FIG. 12 is a perspective view illustrating retainers and rollers moving in the spiral loaded roller rolling path.
- FIGS. 13A and 13B are cross sectional views each illustrating scooping of a roller by a pair of diagonal corresponding parts ( FIG. 13A illustrating the roller that is started to be scooped and FIG. 13B illustrating the roller that is being scooped).
- FIGS. 14A and 14B are perspective views each illustrating a lip portion ( FIG. 14A illustrating combination of the R piece and the end piece and FIG. 14B illustrating the lip portion from which the end piece is removed).
- FIG. 15 is a cross sectional view of an inner wall surface of the lip portion.
- FIG. 16 is a perspective view of the lip portion and diagonal corresponding parts.
- FIG. 17 is a perspective view of another example of the circulation member.
- FIG. 18 is a perspective view of the circulation member (split piece).
- FIG. 19 is a perspective view of a direction change path component.
- FIG. 20 is a perspective view of an R piece.
- FIG. 21 is a perspective view of an end piece.
- FIG. 22 illustrates the R piece and the end piece mounted on the nut.
- FIG. 23 illustrates a structure of the direction change path seen in the axial direction of the screw shaft.
- FIG. 24 is a perspective view illustrating scooping of the roller by lip portion.
- FIG. 25 is a schematic view illustrating scooping of the roller by the lip portion (view seen in the axial direction of the screw shaft).
- FIG. 26 illustrates a direction change path formed in the R piece.
- FIG. 27 illustrates a direction change path formed in the end piece.
- FIGS. 28A and 28B are schematic views illustrating rollers moving on an elevation change ( FIG. 28A illustrating a roller having spherical end surfaces and FIG. 28B illustrating a roller having R-shaped end surfaces).
- FIG. 29 is a perspective view illustrating another example of the lip portion.
- FIG. 30 illustrates scooping of the circulation member seen in the axial direction of the screw shaft (conventional example).
- FIG. 31 is a schematic diagram illustrating contact between the scooping portion and the roller (conventional example).
- FIGS. 1 and 2 are perspective views of a roller screw according to an exemplary embodiment of the present invention.
- FIG. 1 illustrates a perspective view of the roller screw (including a partial cross-sectional view).
- the roller screw has a screw shaft 1 with a spiral roller rolling surface la formed on an outer peripheral surface of the screw shaft and a nut 2 with a spiral loaded roller rolling surface 2 a formed on an inner peripheral surface of the nut opposing the roller rolling surface 1 a.
- the screw shaft 1 is a steel bar made of carbon steel, chrome steel or stainless steel having the spiral roller rolling surface la formed on the outer peripheral surface with a predetermined lead by cutting and grinding or rolling.
- the loaded roller rolling surface 2 a has a V-shaped cross section and its open angle is about 90 degrees.
- two roller rolling surfaces la are formed on the outer peripheral surface of the screw shaft 1 .
- a plurality of rollers is arranged in parallel with each other in each of the two roller rolling surfaces 1 a .
- the axial lines of the rollers arranged in parallel in the two roller rolling surfaces 1 a are opposite to each other. This is to bear loads in the opposite two directions along the axis of the screw shaft.
- two circulation members 3 are provided.
- the number of threads of the roller screw may be determined appropriately, such as one, two or three, depending on the use purpose of the roller screw.
- FIG. 2 is a perspective view of the nut 2 .
- the nut 2 is a cylinder made of carbon steel, chrome steel or stainless steel having the spiral loaded roller rolling surface 2 a formed on the inner peripheral surface with a predetermined lead by cutting and grinding or rolling.
- the loaded roller rolling surface 2 a has a V-shaped cross section and its open angle is about 90 degrees.
- a flange 2 b is formed for mounting the nut 2 on another device.
- FIG. 3 illustrates a roller 4 interposed between the roller rolling surface la of the screw shaft 1 and the loaded roller rolling surface 2 a of the nut 2 .
- the roller 4 is of a cylindrical shape and its diameter is almost the same as the length.
- the shape of the roller 4 seen from the side surface is close to a square.
- the roller 4 has end surfaces 4 a which are chamfered to be spherical with a predetermined curvature radius R. As each of the end surfaces 4 a is spherical, the end surface 4 a of the roller 4 is in contact with the roller rolling surface la at one point.
- the rollers 4 are parallel-arranged with the axis lines of adjacent rollers in parallel with each other. Between the adjacent rollers 4 , a retainer 5 is interposed (see FIG. 12 ). The retainer 5 holds the attitude of each roller 4 in such a manner that the axis line of the roller 4 passes through the center line of the screw shaft 1 .
- the roller 4 bears a load at its side surface 4 a that is in contact with the loaded roller rolling surface 2 a of the nut 2 and the roller rolling surface la of the screw shaft 1 , but it does not bear a load at the end surface 4 a. Therefore, each roller bears the load only in one axial direction of the screw shaft 1 .
- the rollers 4 can bear loads in opposing two directions ((1) and (2)) by differentiating the directions of the axis lines 4 b of the parallel-arranged rollers 4 in the adjacent two loaded roller rolling paths 6 .
- FIG. 4 illustrates a positional relation between the screw shaft 1 and the circulation member 3 mounted on the nut 2 .
- the circulation member 3 has a circulation pipe 8 inserted into a through hole extending in the axial direction of the nut 2 and a pair of direction change path components 12 mounted at the respective ends of the circulation pipe 8 in the axial direction.
- the unloaded return path is formed connecting one end of the loaded roller rolling path 6 to the other.
- the unloaded return path has a straight path formed in the circulation pipe 8 and extending straight in parallel with the center line of the nut 2 (see FIG. 5 ) and a pair of direction change paths 7 connected to both ends of the straight path 9 and formed in the pair of direction change path components 12 (see FIG. 6 ).
- FIG. 5 illustrates the circulation pipe 8 .
- the circulation pipe 8 is formed by combining two split pieces 8 a and 8 b.
- the straight path 9 is formed extending straight in parallel with the axial direction of the nut 2 .
- This straight path 9 is twisted in such a manner that the attitude of each roller 4 moving in the straight path 9 is rotated.
- the roller 4 scooped up from an end of the loaded roller rolling path 6 can be returned to the other end of the loaded roller rolling path 6 with the attitudes of the roller 4 at the respective ends of the loaded roller rolling path 6 match each other.
- the mating surfaces of the split pieces 8 a and 8 b are placed on the diagonal line of the straight path 9 of rectangular cross section. As the straight path 9 is twisted, the mating surfaces 16 of the split pieces 8 a and 8 b are also twisted. At a midpoint of the circulation pipe 8 in the axial direction, the apexes of the rectangle of the mating surfaces 16 are changed. This is to prevent undercut from occurring when the twisted straight path 9 is formed in the split pieces 8 a and 8 b. At each of the both end surfaces of the circulation pipe 8 in the axial direction, a positioning bore 8 c is formed for positioning the circulation pipe 8 .
- FIG. 6 is a perspective view of the direction change path component 12 .
- the direction change path component 12 is mounted on an end surface of the nut 2 .
- the direction change path component 12 is combination of an R piece 10 that forms the inner peripheral side of the direction change path 7 and an end piece 11 that forms the outer peripheral side of the direction change path 7 .
- a continuous path 13 having a V-shaped cross section is formed continuous to the loaded roller rolling surface 2 a of the nut 2 .
- the continuous path 13 extends straight in the tangential direction of the spiral loaded roller rolling surface 2 a.
- the direction change path 7 extends straight in the continuous path 13 and is curved into an arc. In the direction change path 7 , clearance is provided around the rollers 4 .
- the depth of the continuous path 13 is greater than that of the loaded roller rolling surface 2 a of the nut 2 .
- the loaded roller rolling surface 2 a is chamfered.
- a pair of diagonal corresponding parts 14 is formed corresponding to diagonal parts of a rectangular side surface of the roller and jutting toward the screw shaft 1 .
- This paired diagonal corresponding parts 14 function as a scooping portion for scooping the rollers 4 moving in the loaded roller rolling path 6 up into the direction change path 7 .
- a V-shaped mountain-shaped lip portion 15 is formed (see FIG. 7 ) for scooping the retainer 5 out of the circulation raceway up into the unloaded return path.
- a positioning bore 12 a is formed at a joint surface of the direction change path component 12 with the circulation pipe 8 .
- the circulation pipe 8 and the direction change path component 12 can be positioned by inserting positioning pins into the positioning bores 8 c and 12 a of the circulation pipe 8 and the direction change path component 12 , respectively.
- FIG. 7 is a perspective view of the R piece 10 and FIG. 8 is a perspective view of the end piece 11 .
- the direction change path 7 extends straight in the continuous path 13 and then, is curved into an arc.
- the direction change path component 12 is split into the inner peripheral side R piece 10 and the outer peripheral side end piece 11 along the diagonal line of rectangular cross section of the direction change path 7 .
- the R piece 10 has a flange portion 10 a mounted on the end surface of the nut 2 and a main body portion 10 b in which the direction change path is formed. In the flange portion 10 a, a mounting hole 17 is formed for mounting the R piece 10 on the nut 2 .
- the R piece 10 may be manufactured by metal cutting, metal injection molding or resin molding.
- the end piece 11 has a flange portion 11 a to be mounted at an end surface of the nut 2 and a main body portion 11 b where the direction change path 7 is formed.
- a flange portion 11 a to be mounted at an end surface of the nut 2 and a main body portion 11 b where the direction change path 7 is formed.
- one of the paired diagonal corresponding parts 14 for scooping the rollers 4 moving in the loaded roller rolling path 6 is formed.
- a half of the lip portion for scooping up the retainer 5 out of the circulation raceway is formed.
- the end piece 11 may be manufactured by metal cutting, metal injection molding or resin molding.
- FIG. 9 is a perspective view of the nut 2 .
- a through hole 2 c is formed extending straight in parallel with the axis line of the nut 2 .
- the circulation pipe 8 is inserted into the through hole 2 c.
- a recess 2 e is formed which shape matches the flange portions 10 a and 11 a of the direction change path component 12 .
- the R piece 10 and the end piece 11 are put together, their flange portions 10 a and 11 a are fit in the recess 2 e, and a bolt (not shown) is fit in the nut so that the direction change path component 12 can be mounted on the nut 2 .
- FIGS. 10 and 11 illustrate the direction change path component 12 mounted on the end surface 2 d of the nut 2 .
- the mountain-shaped lip portion 15 juts inside of the thread of the loaded roller rolling surface 1 a of the nut 2 , or to the screw shaft 1 side. It is placed to the screw bottom 1 c side rather than the thread lb of the roller rolling surface 1 a of the screw shaft 1 , and it does not come into contact with the screw bottom 1 c .
- the apex 15 a of the lip portion 15 goes along the spiral line of the roller rolling surface 1 a of the screw shaft 1 .
- the curvature radius of the apex 15 a seen in the axial direction of the screw shaft 1 is larger than the radius of the screw bottom 1 c and smaller than the curvature radius of the thread 1 b.
- FIG. 12 illustrates the rollers 4 and the retainer 5 moving in the spiral loaded roller rolling path 6 and being scooped up by a pair of diagonal corresponding parts 14 and the lip portion 15 .
- the width between the paired diagonal corresponding parts 14 becomes narrower as they are deeper in the direction change path 7 .
- the opposed surfaces 12 b of the screw shaft 1 side of the direction change path component 12 is a curved surface that forms a part of the cylinder while the width between the paired diagonal corresponding parts 14 becomes narrower spontaneously by extending the continuous path 13 straight.
- the rollers 4 are guided into the direction change path 7 as they are held at the diagonal parts 4 e by the paired diagonal corresponding parts 14 .
- the retainer 5 interposed between the rollers 4 usually circulates in the same circulation raceway as that of the rollers 4 . However, when there is space between the roller 4 and the retainer 5 , the retainer 5 sometimes gets out of the normal circulation raceway.
- the lip portion 15 scoops the retainer 5 out of the circulation raceway and guides it into the direction change path 7 .
- the inner wall surface 15 b of the lip portion 15 is away from the raceway of the rollers and is kept out of contact with the rollers 4 . Therefore, the rollers 4 are in contact with the edge 15 c at the loaded roller rolling path side of the lip portion 15 and the edge 15 c can be prevented from being broken.
- FIGS. 13A and 13B illustrate scooping of the roller 4 by the paired diagonal corresponding parts 14 ( FIG. 13A illustrating the roller 4 that is started to be scooped and FIG. 13B illustrating the roller 4 that is being scooped).
- the diagonal corresponding parts 14 provided in the R piece 10 and end piece 11 sandwich the diagonal parts 4 e of the roller and guide it into the direction change path 7 .
- the width between the paired diagonal corresponding parts 14 becomes gradually narrower as it goes deeper inside of the direction change path 7 in such a manner that the cross section of the direction change path 7 formed by the continuous path 13 and the paired diagonal corresponding parts 14 becomes close to a rectangle gradually. Therefore, the contact surface between the diagonal part 4 e of the roller 4 and the diagonal corresponding part 14 becomes gradually larger and the roller 4 can come into the inside of the direction change path 7 easily.
- FIGS. 14A and 14B illustrate a lip portion 15 .
- FIG. 14A illustrates combined R piece 10 and end piece 11
- FIG. 14B illustrates the lip portion 15 from which the end piece 11 is removed.
- the inner wall surface 15 b of the lip portion is formed to be tapered in a side surface 31 a that forms a virtual trial pole of FIG. 14B .
- the inner wall surface 15 b of the lip portion 15 is tapered in such a manner that the cross sectional area of the direction change path 7 becomes gradually larger from the direction change path 7 to the loaded roller rolling path 6 . This is to prevent the rollers 4 from coming into contact with the inner wall surface 15 b of the lip portion 15 .
- the inner wall surface 15 b of the lip portion 15 is tapered, the apex of the edge of the lip portion 15 may be sometimes displaced.
- FIG. 15 illustrates a cross section of the inner wall surface 15 b of the lip portion 15 .
- the above-described tapered inner wall surface 15 b of the lip portion 15 is formed into V shape in such a manner that an apex angle a formed by connecting the inner walls of the paired diagonal corresponding parts 14 and an apex 33 on the diagonal line 32 connecting diagonal parts 4 f of the roller 4 scooped by the paired diagonal corresponding parts 14 , which diagonal parts 4 f are out of contact with the paired diagonal corresponding parts, is less than 90 degrees.
- FIG. 16 is a detail perspective view of the lip portion and the diagonal corresponding parts 14 .
- the roller 4 is scooped up by the diagonal corresponding parts 14 formed at the end of the continuous path 13 .
- the width between the paired diagonal corresponding parts 14 becomes narrower as they are deeper in the continuous path 13 and finally they are connected to each other with no space therebetween.
- the retainer 5 away from the circulation raceway is scooped up into the direction change path 7 in contact with the inner wall surface 15 b of the lip portion 15 .
- the roller does not come into contact with the inner wall surface 15 b of the lip portion 15 .
- the dashed line in the figure indicates the boundary between the arc part and the straight part of the continuous path 13 .
- FIGS. 17 and 18 illustrate other examples of the circulation member to be mounted on the nut 2 .
- the circulation member 3 has a circulation pipe 108 to be inserted into a through hole extending in the axial direction of the nut 2 and a pair of direction change path components to be mounted to the respective ends of the circulation pipe 108 in the axial direction.
- an unloaded return path is formed connecting one end of the loaded roller rolling path 6 to the other.
- the unloaded return path has a straight path 109 extending straight in parallel with the center line of the nut 2 (see FIG. 23 ) and a pair of curved direction change paths which are connected to the respective ends of the straight path 109 and formed in the paired direction change path components 112 .
- the circulation pipe 108 is combination of two split pieces 108 a and 108 b.
- FIG. 18 illustrates the circulation pipe 108 from which one split piece 108 b is removed.
- a straight path 109 is formed straight in parallel with the axial direction of the nut 2 .
- This straight path 109 is twisted so that the attitude of each roller 4 moving in the straight path 109 can be rotated.
- As the attitude of the roller is rotated in the straight path 109 it becomes possible to return the roller 4 scooped from an end of the loaded roller rolling path 6 to the other end of the loaded roller rolling path 6 with the attitudes of the roller 4 at the respective ends of the loaded roller rolling path 6 matched to each other.
- the mating surfaces of the split pieces 108 a and 108 b are on the diagonal line of the straight path 109 of rectangular cross section. As the straight path 109 is twisted, the apexes of the rectangle for the mating surfaces 116 are changed at a midpoint in the axial direction of the circulation pipe 108 . This is to prevent occurrence of undercut when the twisted straight path 109 is formed in the split pieces 108 a and 108 b . In each end surface of the circulation pipe 108 in the axial direction, a positioning hole is formed for positioning of the circulation pipe.
- the direction change path component 112 is mounted on an end surface of the nut 2 .
- FIG. 19 illustrates a perspective view of the direction change path component.
- the direction change path component 112 has combination of an R piece 110 that forms the inner peripheral side of the direction change path and an end piece 111 that forms the outer peripheral side of the direction change path 107 .
- a V-shaped mountain-like lip portion 114 is provided which juts toward the roller rolling surface la of V-shaped cross section of the screw shaft 1 and scoops the rollers 4 moving in the loaded roller rolling path 6 up into the direction change path.
- the edge 114 a of the lip portion 114 is placed close to the roller rolling surface la of V-shaped cross section of the screw shaft 1 .
- the end 107 e of the direction change path 107 at the opposite side to the lip portion 114 is continuous to the loaded roller rolling surface 2 a of V-shaped cross section of the nut 2 .
- a positioning bore 115 is formed in the contact surface 112 a of the direction change path component 112 with the circulation pipe 108 . As a positioning pin is inserted into the positioning bore 115 of the direction change path component 112 and the circulation pipe 108 , they can be positioned.
- FIG. 20 is a perspective view of the R piece 110 and FIG. 21 is a perspective view of the end piece 111 .
- the direction change path 107 is curved, but not twisted.
- the direction change path component 112 is divided into the inner peripheral side R piece 110 and the outer peripheral side end piece 111 along the diagonal line of the direction change path 107 of rectangular cross section.
- the R piece 110 has a flange portion 110 a for mounting on the end surface of the nut 2 and a main body portion 110 b where the direction change path 107 is formed.
- a mounting hole 117 is formed for mounting the R piece 110 on the nut 2 .
- the R piece 110 may be manufactured by metal cutting or resin molding.
- the end piece 111 has a flange portion 111 a which is mounted on the end surface of the nut 2 and a main body portion 111 b with the direction change path 107 formed therein.
- a half of the lip portion 114 for scooping up the rollers 4 moving in the loaded roller rolling path 6 is formed.
- the end piece 111 may be formed by cutting of metal or resin molding.
- the R piece 110 and the end piece 111 are superposed together a bolt (not shown) is inserted into their flange portions 110 a and 111 a and the bolt is fit in the end surface of the nut 2 thereby to mount the direction change path component 112 on the nut 2 .
- the lip portion 114 is placed inside of the thread 1 c of the roller rolling surface 1 a of the screw shaft, however, it does not come into contact with the screw bottom ld of the roller rolling surface 1 a.
- FIG. 23 illustrates a structure of the direction change path 107 seen in the axial direction of the screw shaft 1 .
- the end piece 111 is removed.
- the chain double-dashed line in the figure indicates the center line 107 a of the direction change path 107 and the broken line indicates the tangential direction 6 a of the loaded roller rolling path 6 .
- the direction change path 107 has a scooping path 107 b where a lip portion 114 is formed.
- the center line 107 a of the scooping path 107 b connected to the loaded roller rolling path 6 is placed outside of the tangential direction 6 a of the center line 6 b of the loaded roller rolling path 6 , that is, inside of the nut 2 .
- the moving direction inside the scooping path 107 b of each roller 4 moving from the loaded roller rolling path 6 to the scooping path 107 b is directed to the outside of the tangential direction of the loaded roller rolling path 6 .
- the direction change path 107 is curved into an arc at a midpoint to the straight line 109 and is connected to the end of the straight path 109 .
- the roller 4 is moved along the center line 107 thereby to be able to design the direction change path 107 .
- the center line 10 of the direction change path 107 seen in the side surface direction of the screw shaft 1 is direction in the lead direction of the screw shaft 1 .
- each roller 4 inside the scooping portion 107 b is directed outside of the tangential direction 6 a, the edge 114 a of the lip portion 114 can be extended toward the loaded roller rolling path 6 while the enough thickness of the lip portion 114 is assured.
- the unconstrained area of the roller 4 from the loaded roller rolling path 6 into the lip portion 114 is shortened and it becomes possible to prevent skewing of the roller 4 in the unconstrained area.
- FIG. 24 illustrates the raceway of each roller 4 scooped up by the lip portion 114 .
- the roller 4 rolls in line contact with the two points of the roller rolling surface la of the screw shaft 1 and the loaded roller rolling surface 2 a of the nut 2 .
- the roller 4 Once the roller 4 is moved up to an end of the loaded roller rolling path 6 , it enters the lip portion 114 .
- the roller 4 Once the roller 4 gets out of the loaded roller rolling path 6 , its end in the moving direction enters the lip portion 114 .
- FIG. 24 illustrates the raceway of each roller 4 scooped up by the lip portion 114 .
- the edge 114 of the lip portion 114 covers the end of the roller 4 in the moving direction.
- the distance L 1 from the boundary 120 between the loaded roller rolling path and the unloaded return path to the lip portion 114 is smaller than the radius of the roller 4 .
- the angle ⁇ 1 of the center line 107 a of the scooping path 107 b relative to the tangential direction 6 a is set to such an angle that the edge 114 a of the lip portion 114 covers the end of the roller 4 in the moving direction.
- the roller 4 enters the lip portion 114 while it keeps the attitude inside the loaded roller rolling path 6 . Therefore, it is possible to prevent skewing of the roller 4 moving from the loaded roller rolling path 6 to the lip portion 114 .
- the edge 114 a of the lip portion 114 is out of contact with the roller 4 . Therefore, it is possible to prevent damage to the edge 114 a of the lip portion 114 .
- the inner wall surface of the lip portion 114 comes into contact with the side surface of the roller 4 and it guides the roller 4 into the direction change path 107 .
- FIGS. 26 and 27 illustrate the direction change path 107 formed in the R piece 110 and the end piece 111 .
- the direction change path 107 of the R piece 110 and the end piece 111 has the scooping portion 107 b directed outside of the tangential direction 6 a of the loaded roller rolling path 6 , a bent intermediate path 107 c and a communication path 107 d connecting the intermediate path 107 c to the straight path 109 .
- FIGS. 28A and 28B are side views of a roller 4 , 121 moving in the circulation path.
- the roller 4 in FIG. 28A has spherical end surfaces and the roller 121 in FIG. 28B has circularly chamfered end surfaces 121 a.
- the roller 121 with chamfered end surfaces is used to circulate, it is constrained at the edge 114 a of the lip portion 114 more securely. This reveals that the roller 4 can move smoothly when it has spherical end surfaces.
- the curvature radius of the end surface 4 a becomes larger than that of the circularly-chamfered roller 4 .
- Inclination of the tangential direction 4 f of the end surface 4 a at the elevation change can be smaller than the inclination 121 e of the roller 121 also when the roller moves on the elevation change between the components. Hence, the roller 4 is prevented from being caught in the elevation difference.
- the roller 4 becomes easy to be inclined and therefore, it is preferable that the retainer is interposed between adjacent rollers 4 to prevent skewing.
- FIG. 29 illustrates another example of the lip portion 114 .
- the lip portion 114 forms a mountain by combining a first wall part 126 b and a second wall part 126 a at the apex 126 c .
- the first wall part 126 b is positioned to the end surface side of the roller and the second wall part 126 a is positioned to the side surface side of the roller 4 .
- the first wall part 126 b is cut short.
- the edge 128 b of the first wall part 126 b is shifted from the edge 128 a of the second wall part 126 a, which starts at the apex 126 c, and the edge 128 b is away from the loaded roller rolling path 6 more than the edge 128 a of the second wall part 126 a.
- the length of the lip portion 114 is differentiated between the end surface side and side surface side of the roller 4 , it becomes possible to constrain first the side surface of the roller 4 and then the end surface of the roller 4 .
- the lip portion 114 may be damaged.
- the side surface of the roller 4 is first constrained and then, after the angle of the end surface of the roller 4 is maintained constant the end surface of the roller 4 is constrained thereby to prevent damage to the lip portion 114 .
- the present invention is not limited to the above-mentioned exemplary embodiments and may be embodied in various forms without departing from the scope of the invention.
- the continuous path of the direction change path component may extend directed outside not of the tangential direction of the loaded roller rolling path of the nut, but of tangential direction seen in the axial direction of the nut.
- the circulation member is not limited to such an endcap type circulation member as in the embodiments and may be a return pipe formed by bending both ends of a pipe.
- the rollers may be parallel-arranged with axis lines of the adjacent rollers kept in parallel with each other, or may be cross-arranged with the axis lines orthogonal to each other.
- Each roller used may be a tapered roller having tapered side surfaces instead of a cylindrical roller.
- the axis lines of plural rollers parallel-arranged in the respective two roller rolling surfaces may be directed in the same direction.
- the scooping portion may not be the lip portion jutting to the screw shaft side as described above but a boat-bottom shaped scooping portion for scooping the parts on the diagonal line of the roller as a boat-bottom scooping of a ball screw.
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Abstract
Description
- The present invention relates to a roller screw having rollers movably interposed between a screw shaft and a nut.
- Recently, there has been developed a roller screw having rollers movably interposed between a screw shaft and a nut. As each roller is in line contact with a roller rolling surface, the roller screw has the advantage of larger load to bear as compared with a ball screw. However, although a ball can roll in every direction, the roller can move only in one direction and therefore, there is a problem that the roller is very difficult to circulate.
- The roller screw has a circulation path having a spiral loaded roller rolling path between a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft and a spiral loaded roller rolling surface formed on an inner peripheral surface of the nut and an unloaded return path connecting one end of the loaded roller rolling path to the other end. The unloaded return path is formed in a circulation member which is mounted on the nut. In the circulation member, a lip portion for scooping rollers moving on the roller rolling surface of the screw shaft is provided as a scooping portion for scooping the roller rolling on the spiral loaded roller rolling path. The lip portion juts from the nut toward the roller rolling surface of the screw shaft.
- In the unloaded return path, clearance is provided around the rollers and the diameter of the unloaded return path is larger than the diameter of the loaded roller rolling path. In a conventional roller screw, in order to make up for a difference between diameters of the unloaded return path and the loaded roller rolling path, the inner wall surface of the lip portion of the circulation member is formed tapered with the width that gradually becomes narrower from the unloaded return path toward the loaded roller rolling path (see patent document 1). Then, the rollers moving in the unloaded return path are first aligned to be guided to the loaded roller rolling path.
- As described above, the rollers moving in the spiral loaded roller rolling path are scooped by the scooping portion of the circulation member and guided into the unloaded return path. In the conventional roller screw, in order to smoothly scoop each roller moving on the loaded roller rolling path, the unloaded return path where the scooping portion is formed is arranged in the tangential direction of the loaded roller rolling path (see patent document 2). That is, it is arranged in the tangential direction of the circular loaded roller rolling path seen in the axial direction of the nut and in the lead angle direction of the loaded roller rolling path seen in the side surface direction of the nut.
- [Patent document 1] Japanese Patent Application Laid-Open No. 2006-118649
[Patent document 2] Japanese Patent Application Laid-Open No. 11-210858 - However, the rollers move from the loaded roller rolling path to the unloaded return path. If the rollers are scooped up by the lip portion with the narrowed entry, sometimes the rollers may fall to the roller rolling surface side of the screw shaft, come into collision with the edge of the lip portion and cannot be scooped up well. If the rollers come into collision with the edge of the lip portion, the edge of the lip portion may be broken or the rollers may be jammed.
- In addition, as illustrated in
FIG. 30 , if the unloaded return path is arranged in the tangential direction of the loaded roller rolling path, a scoopingportion 132 of thecirculation member 131 cannot be close to the loadedroller rolling path 133. This is because, if it is arranged too closer, it is difficult to keep enough thickness to assure enough strength in order to prevent the scoopingportion 132 from coming into contact with the screw shaft. Therefore, there is generated an unconstrained area from when therollers 134 get out of the loadedroller rolling path 133 to when they are constrained by the scoopingportion 132. In this unconstrained area, the rollers maybe skewed, and as illustrated inFIG. 31 , the end of the side surface of each of therollers 134 in the axial direction may come into collision with the edge of thescooping portion 132. Theroller 134 moving from the loaded roller rolling path to the unloaded return path comes into the scooping portion while it is pushed by the followingroller 134. When theroller 134 is in collision with the edge of thescooping portion 132, the edge of the scoopingportion 132 may be broken or therollers 134 may be jammed. - Then, the present invention provides a roller screw capable of preventing rollers moving from an unloaded return path to a loaded roller rolling path from coming into collision with a scooping portion.
- Further, the present invention has another object to provide a roller screw capable of preventing skewing of rollers moving from the unloaded return path to the loaded roller rolling path and enabling smooth movement of the rollers.
- The present invention will be explained below.
- In order to solve the above-mentioned problems, the invention of
claim 1 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping portion, provided in the circulation member, for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, the scooping portion having a pair of diagonal corresponding parts that are in contact with diagonal parts of a rectangular side surface of each of the rollers, a width between the diagonal corresponding parts becoming gradually narrower as the diagonal corresponding parts are deeper in the unloaded return path in such a manner that a cross section of the unloaded return path is closer to a rectangle, and the rollers that move from the loaded roller rolling path to the unloaded return path being scooped up into the unloaded return path while the diagonal parts of each of the rollers are held by the diagonal corresponding parts. - The invention of
claim 2 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping portion, provided in the circulation member, for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, the scooping portion having a pair of diagonal corresponding parts which jut toward the screw shaft from an edge of a continuous path of V shaped cross section connected to the loaded roller rolling surface of the nut and which correspond to diagonal parts of a rectangular side surface of each of the rollers, and a width between the diagonal corresponding parts becoming gradually narrower as the diagonal corresponding parts are deeper in the unloaded return path in such a manner that a cross section of the unloaded return path formed by the diagonal corresponding parts and the continuous path is gradually closer to a rectangle in accordance with a deepness of the unloaded return path. - The invention of
claim 3 is characterized in that in the roller screw ofclaim - The invention of
claim 4 is characterized in that in the roller screw ofclaim 3, the inner wall surfaces of the lip portion has a cross section orthogonal to the unloaded return path, which cross section is V shaped in such a manner that an apex angle a formed by connecting the inner wall surfaces of the diagonal corresponding parts and an apex on a diagonal line connecting diagonal parts, out of contact with the diagonal corresponding parts, of each of the rollers scooped by the diagonal corresponding parts is less than 90 degrees. - The invention of
claim 5 is characterized in that in the roller screw ofclaim - The invention of
claim 6 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping path provided in the unloaded return path and having a scooping portion for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, a moving direction in the scooping path of each of the rollers moving from the loaded roller rolling path to the unloaded return path being outside of a tangential direction of the loaded roller rolling path when seen in an axial direction of the nut. - The invention of
claim 7 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping path provided in the unloaded return path circulation member and having a scooping portion for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, a center line of the scooping path being outside of a tangential direction of the loaded roller rolling path when seen in an axial direction of the nut. - The invention of
claim 8 is characterized in that in the roller screw ofclaim - The invention of
claim 9 is a roller screw comprising: a screw shaft having a spiral roller rolling surface formed on an outer peripheral surface of the screw shaft; a nut having a loaded roller rolling surface formed in an inner peripheral surface of the nut, facing the roller rolling surface of the screw shaft; a circulation member provided on the nut and having an unloaded return path connecting one end of the loaded roller rolling surface of the nut to an opposite end thereof; a plurality of rollers arranged in a loaded roller rolling path between the roller rolling surface of the screw shaft and the loaded roller rolling surface of the nut and in the unloaded return path of the circulation member; and a scooping portion, provided in the circulation member, for scooping the rollers moving in the loaded roller rolling path up into the unloaded return path, and the scooping portion covering each of the rollers when a center of the roller is positioned at a boundary between the loaded roller rolling path and the unloaded return path. - The invention of
claim 10 is characterized in that in the roller screw ofclaim 9, the unloaded return path has a scooping path where the scooping portion is formed, and a moving direction in the scooping path of each of the rollers moving from the loaded roller rolling path to the unloaded return path is outside of a tangential direction of the loaded roller rolling path when seen in an axial direction of the nut. - The invention of
claim 11 is characterized in that in the roller screw ofclaim - The invention of
claim 12 is characterized in that in the roller screw ofclaim - According to the invention of
claim 1, it is possible to scoop each roller by the diagonal corresponding parts of the scooping portion holding diagonal parts of the roller. As no lip portion needs to be provided at the scooping portion, there is no fear of breakage of the lip portion. - According to the invention of
claim 2, it is possible to scoop each roller by the diagonal corresponding parts of the scooping portion holding diagonal parts of the roller. As no lip portion needs to be provided at the scooping portion, there is no fear of breakage of the lip portion. - According to the invention of
claim 3, it is possible to scoop up a retainer that is out of a circulation raceway by the retainer-scooping lip portion. As this lip portion is provided away from the raceway of the rollers and is out of contact with the rollers, the lip portion can be prevented from being broken by contact with the rollers. - According to the invention of
claim 4, it is possible to keep the inner wall surface of the lip portion away from the rollers. - According to the invention of
claim 5, it is possible to keep the screw-shaft side edge of the lip portion out of the rollers. Besides, it is possible to guide the retainer scooped by the retainer scooping lip portion into the unloaded return path smoothly. - According to the invention of
claim 6, as the moving direction of the rollers in the scooping path is placed outside the tangential direction of the loaded roller rolling oath, it is possible to make the edge of the scooping portion close to the loaded roller rolling path while keeping enough thickness of the scooping portion. As the area to constrain the rollers by the scooping portion is longer and the area not to constrain the rollers is shorter, it is possible to prevent skewing of the rollers. - According to the invention of
claim 7, as the moving direction of the rollers in the scooping path is placed outside the tangential direction of the loaded roller rolling oath, it is possible to make the edge of the scooping portion close to the loaded roller rolling path while keeping enough thickness of the scooping portion. As the area to constrain the rollers by the scooping portion is longer and the area not to constrain the rollers is shorter, it is possible to prevent skewing of the rollers. - According to the invention of
claim 8, it is possible to connect the scooping path directed outside of the tangential direction with the straight path. - According to the invention of
claim 9, the end part of each roller in the moving direction comes into the scooping portion of the circulation member before the roller gets out of the loaded roller rolling path completely. Therefore, it is possible to eliminate the area not to constrain the roller. - According to the invention of
claim 10, as the moving direction of each roller in the unloaded return path is placed outside of the tangential direction of the loaded roller rolling path, it is possible to make the edge of the scooping portion close to the loaded roller rolling path while keeping enough thickness of the scooping portion. - According to the invention of
claim 11, it is possible to prevent the end surface of each roller from being caught in the edge of the scooping portion when the roller enters the scooping portion of the circulation member. It is also possible to prevent the end surface of the roller being caught in an elevation change even when the roller passes through the elevation change between the components. - According to the invention of
claim 12, as the side surface of each roller is first constrained by the lip portion, the end surface of the roller abuts against the edge of the lip portion and the lip portion can be prevented from being damaged. -
FIG. 1 is a perspective view of a roller screw according to an exemplary embodiment of the present invention. -
FIG. 2 is a perspective view of a nut of the above-mentioned roller screw. -
FIG. 3 is a side view illustrating a roller sandwiched between a screw shaft and the nut. -
FIG. 4 is a perspective view of the screw shaft and a circulation member. -
FIG. 5 is a perspective view of a circulation pipe. -
FIG. 6 is a perspective view of a direction change path component. -
FIG. 7 is a perspective view of an R piece. -
FIG. 8 is a perspective view of an end piece. -
FIG. 9 is a perspective view of the nut into which the circulation pipe is inserted. -
FIG. 10 is a perspective view of the nut on which the direction change path component is mounted. -
FIG. 11 is a front view of the nut on which the direction change path component is mounted. -
FIG. 12 is a perspective view illustrating retainers and rollers moving in the spiral loaded roller rolling path. -
FIGS. 13A and 13B are cross sectional views each illustrating scooping of a roller by a pair of diagonal corresponding parts (FIG. 13A illustrating the roller that is started to be scooped andFIG. 13B illustrating the roller that is being scooped). -
FIGS. 14A and 14B are perspective views each illustrating a lip portion (FIG. 14A illustrating combination of the R piece and the end piece andFIG. 14B illustrating the lip portion from which the end piece is removed). -
FIG. 15 is a cross sectional view of an inner wall surface of the lip portion. -
FIG. 16 is a perspective view of the lip portion and diagonal corresponding parts. -
FIG. 17 is a perspective view of another example of the circulation member. -
FIG. 18 is a perspective view of the circulation member (split piece). -
FIG. 19 is a perspective view of a direction change path component. -
FIG. 20 is a perspective view of an R piece. -
FIG. 21 is a perspective view of an end piece. -
FIG. 22 illustrates the R piece and the end piece mounted on the nut. -
FIG. 23 illustrates a structure of the direction change path seen in the axial direction of the screw shaft. -
FIG. 24 is a perspective view illustrating scooping of the roller by lip portion. -
FIG. 25 is a schematic view illustrating scooping of the roller by the lip portion (view seen in the axial direction of the screw shaft). -
FIG. 26 illustrates a direction change path formed in the R piece. -
FIG. 27 illustrates a direction change path formed in the end piece. -
FIGS. 28A and 28B are schematic views illustrating rollers moving on an elevation change (FIG. 28A illustrating a roller having spherical end surfaces andFIG. 28B illustrating a roller having R-shaped end surfaces). -
FIG. 29 is a perspective view illustrating another example of the lip portion. -
FIG. 30 illustrates scooping of the circulation member seen in the axial direction of the screw shaft (conventional example). -
FIG. 31 is a schematic diagram illustrating contact between the scooping portion and the roller (conventional example). - 1 . . . screw shaft, 1 a . . . roller rolling surface, 2 . . . nut, 2 a . . . loaded roller rolling surface, 3 . . . circulation member, 4 . . . roller, 4 a . . . end surface, 4 e . . . diagonal part, 5 . . . retainer, 6 . . . loaded roller rolling path, 6 a . . . tangential direction of loaded roller rolling path, 7 . . . direction change path, 12 . . . direction change path component, 13 . . . continuous path, 14 . . . diagonal corresponding part, 15 . . . lip portion, 15 b . . . inner wall surface, 32 . . . diagonal line, 33 . . . apex, α. . . apex angle, 107 . . . direction change path, 107 a . . . center line of direction change path, 107 b . . . scooping path, 110 . . . R piece, 111 . . . end piece, 112. . . direction change path component, 114 . . . lip portion (scooping portion), 114 a . . . edge
-
FIGS. 1 and 2 are perspective views of a roller screw according to an exemplary embodiment of the present invention.FIG. 1 illustrates a perspective view of the roller screw (including a partial cross-sectional view). - The roller screw has a
screw shaft 1 with a spiral roller rolling surface la formed on an outer peripheral surface of the screw shaft and anut 2 with a spiral loadedroller rolling surface 2 a formed on an inner peripheral surface of the nut opposing theroller rolling surface 1 a. - The
screw shaft 1 is a steel bar made of carbon steel, chrome steel or stainless steel having the spiral roller rolling surface la formed on the outer peripheral surface with a predetermined lead by cutting and grinding or rolling. The loadedroller rolling surface 2 a has a V-shaped cross section and its open angle is about 90 degrees. In this embodiment, two roller rolling surfaces la are formed on the outer peripheral surface of thescrew shaft 1. Then, a plurality of rollers is arranged in parallel with each other in each of the tworoller rolling surfaces 1 a. The axial lines of the rollers arranged in parallel in the tworoller rolling surfaces 1 a are opposite to each other. This is to bear loads in the opposite two directions along the axis of the screw shaft. In order to circulate the rollers moving in the tworoller rolling surfaces 1 a, twocirculation members 3 are provided. Needless to say, the number of threads of the roller screw may be determined appropriately, such as one, two or three, depending on the use purpose of the roller screw. -
FIG. 2 is a perspective view of thenut 2. Thenut 2 is a cylinder made of carbon steel, chrome steel or stainless steel having the spiral loadedroller rolling surface 2 a formed on the inner peripheral surface with a predetermined lead by cutting and grinding or rolling. The loadedroller rolling surface 2 a has a V-shaped cross section and its open angle is about 90 degrees. At the end of the outer periphery of thenut 2 in the axial direction, aflange 2 b is formed for mounting thenut 2 on another device. -
FIG. 3 illustrates aroller 4 interposed between the roller rolling surface la of thescrew shaft 1 and the loadedroller rolling surface 2 a of thenut 2. Theroller 4 is of a cylindrical shape and its diameter is almost the same as the length. The shape of theroller 4 seen from the side surface is close to a square. Theroller 4 hasend surfaces 4 a which are chamfered to be spherical with a predetermined curvature radius R. As each of the end surfaces 4 a is spherical, theend surface 4 a of theroller 4 is in contact with the roller rolling surface la at one point. In each of the two loadedroller rolling paths 6 between the loadedroller rolling surfaces 2 a of thenut 2 and the roller rolling surfaces la of thescrew shaft 1, therollers 4 are parallel-arranged with the axis lines of adjacent rollers in parallel with each other. Between theadjacent rollers 4, aretainer 5 is interposed (seeFIG. 12 ). Theretainer 5 holds the attitude of eachroller 4 in such a manner that the axis line of theroller 4 passes through the center line of thescrew shaft 1. - The
roller 4 bears a load at itsside surface 4 a that is in contact with the loadedroller rolling surface 2 a of thenut 2 and the roller rolling surface la of thescrew shaft 1, but it does not bear a load at theend surface 4 a. Therefore, each roller bears the load only in one axial direction of thescrew shaft 1. Therollers 4 can bear loads in opposing two directions ((1) and (2)) by differentiating the directions of theaxis lines 4 b of the parallel-arrangedrollers 4 in the adjacent two loadedroller rolling paths 6. -
FIG. 4 illustrates a positional relation between thescrew shaft 1 and thecirculation member 3 mounted on thenut 2. Thecirculation member 3 has acirculation pipe 8 inserted into a through hole extending in the axial direction of thenut 2 and a pair of direction changepath components 12 mounted at the respective ends of thecirculation pipe 8 in the axial direction. In thecirculation member 3, the unloaded return path is formed connecting one end of the loadedroller rolling path 6 to the other. The unloaded return path has a straight path formed in thecirculation pipe 8 and extending straight in parallel with the center line of the nut 2 (seeFIG. 5 ) and a pair ofdirection change paths 7 connected to both ends of thestraight path 9 and formed in the pair of direction change path components 12 (seeFIG. 6 ). Once eachroller 4 rolls up to an end of the loadedroller rolling path 6, theroller 4 is guided into the direction changepath 7 of thecirculation member 3. After passing through thestraight path 9, theroller 4 is returned from the other direction changepath 7 back to the other end of the loadedroller rolling path 6. -
FIG. 5 illustrates thecirculation pipe 8. Thecirculation pipe 8 is formed by combining twosplit pieces circulation pipe 8, thestraight path 9 is formed extending straight in parallel with the axial direction of thenut 2. Thisstraight path 9 is twisted in such a manner that the attitude of eachroller 4 moving in thestraight path 9 is rotated. As the attitude of the roller is rotated in thestraight path 9, theroller 4 scooped up from an end of the loadedroller rolling path 6 can be returned to the other end of the loadedroller rolling path 6 with the attitudes of theroller 4 at the respective ends of the loadedroller rolling path 6 match each other. - The mating surfaces of the
split pieces straight path 9 of rectangular cross section. As thestraight path 9 is twisted, the mating surfaces 16 of thesplit pieces circulation pipe 8 in the axial direction, the apexes of the rectangle of the mating surfaces 16 are changed. This is to prevent undercut from occurring when the twistedstraight path 9 is formed in thesplit pieces circulation pipe 8 in the axial direction, apositioning bore 8 c is formed for positioning thecirculation pipe 8. -
FIG. 6 is a perspective view of the direction changepath component 12. The directionchange path component 12 is mounted on an end surface of thenut 2. The directionchange path component 12 is combination of anR piece 10 that forms the inner peripheral side of the direction changepath 7 and anend piece 11 that forms the outer peripheral side of the direction changepath 7. - In the direction change
path component 12, acontinuous path 13 having a V-shaped cross section is formed continuous to the loadedroller rolling surface 2 a of thenut 2. Thecontinuous path 13 extends straight in the tangential direction of the spiral loadedroller rolling surface 2 a. Thedirection change path 7 extends straight in thecontinuous path 13 and is curved into an arc. In the direction changepath 7, clearance is provided around therollers 4. The depth of thecontinuous path 13 is greater than that of the loadedroller rolling surface 2 a of thenut 2. In order to prevent an elevation change from occurring at a connecting portion between the loadedroller rolling surface 2 a and thecontinuous path 13, the loadedroller rolling surface 2 a is chamfered. - At an edge of the
continuous path 13, a pair of diagonalcorresponding parts 14 is formed corresponding to diagonal parts of a rectangular side surface of the roller and jutting toward thescrew shaft 1. This paired diagonalcorresponding parts 14 function as a scooping portion for scooping therollers 4 moving in the loadedroller rolling path 6 up into the direction changepath 7. Between the paired diagonalcorresponding parts 14, a V-shaped mountain-shapedlip portion 15 is formed (seeFIG. 7 ) for scooping theretainer 5 out of the circulation raceway up into the unloaded return path. When the direction changepath component 12 is mounted on thenut 2, the structures of these paired diagonalcorresponding parts 14 andlip portion 15 will be described later. - At a joint surface of the direction change
path component 12 with thecirculation pipe 8, a positioning bore 12 a is formed. Thecirculation pipe 8 and the direction changepath component 12 can be positioned by inserting positioning pins into the positioning bores 8 c and 12 a of thecirculation pipe 8 and the direction changepath component 12, respectively. -
FIG. 7 is a perspective view of theR piece 10 andFIG. 8 is a perspective view of theend piece 11. As described above, the direction changepath 7 extends straight in thecontinuous path 13 and then, is curved into an arc. The directionchange path component 12 is split into the inner peripheralside R piece 10 and the outer peripheralside end piece 11 along the diagonal line of rectangular cross section of the direction changepath 7. As illustrated inFIG. 7 , theR piece 10 has aflange portion 10 a mounted on the end surface of thenut 2 and amain body portion 10 b in which the direction change path is formed. In theflange portion 10 a, a mountinghole 17 is formed for mounting theR piece 10 on thenut 2. At a part of theflange portion 10 where thecontinuous path 13 is formed, one of the paired diagonalcorresponding parts 14 for scooping up therollers 4 moving in the loadedroller rolling path 6 is formed. Besides, in the diagonalcorresponding part 14, a half of thelip portion 15 is formed for scooping up theretainer 5 out of the circulation raceway. TheR piece 10 may be manufactured by metal cutting, metal injection molding or resin molding. - As illustrated in
FIG. 8 , theend piece 11 has aflange portion 11 a to be mounted at an end surface of thenut 2 and amain body portion 11 b where the direction changepath 7 is formed. In apart of theflange portion 11 a where thecontinuous path 13 is formed, one of the paired diagonalcorresponding parts 14 for scooping therollers 4 moving in the loadedroller rolling path 6 is formed. Besides, in the diagonalcorresponding part 14, a half of the lip portion for scooping up theretainer 5 out of the circulation raceway is formed. Theend piece 11 may be manufactured by metal cutting, metal injection molding or resin molding. -
FIG. 9 is a perspective view of thenut 2. In thenut 2, a throughhole 2 c is formed extending straight in parallel with the axis line of thenut 2. Thecirculation pipe 8 is inserted into the throughhole 2 c. Besides, in anend surface 2 d of thenut 2 in the axial direction, arecess 2 e is formed which shape matches theflange portions path component 12. TheR piece 10 and theend piece 11 are put together, theirflange portions recess 2 e, and a bolt (not shown) is fit in the nut so that the direction changepath component 12 can be mounted on thenut 2. -
FIGS. 10 and 11 illustrate the direction changepath component 12 mounted on theend surface 2 d of thenut 2. When the direction changepath component 12 is mounted on thenut 2, the mountain-shapedlip portion 15 juts inside of the thread of the loadedroller rolling surface 1 a of thenut 2, or to thescrew shaft 1 side. It is placed to thescrew bottom 1 c side rather than the thread lb of theroller rolling surface 1 a of thescrew shaft 1, and it does not come into contact with thescrew bottom 1 c. The apex 15 a of thelip portion 15 goes along the spiral line of theroller rolling surface 1 a of thescrew shaft 1. The curvature radius of the apex 15 a seen in the axial direction of thescrew shaft 1 is larger than the radius of thescrew bottom 1 c and smaller than the curvature radius of thethread 1 b. -
FIG. 12 illustrates therollers 4 and theretainer 5 moving in the spiral loadedroller rolling path 6 and being scooped up by a pair of diagonalcorresponding parts 14 and thelip portion 15. The width between the paired diagonalcorresponding parts 14 becomes narrower as they are deeper in the direction changepath 7. The opposed surfaces 12 b of thescrew shaft 1 side of the direction changepath component 12 is a curved surface that forms a part of the cylinder while the width between the paired diagonalcorresponding parts 14 becomes narrower spontaneously by extending thecontinuous path 13 straight. Therollers 4 are guided into the direction changepath 7 as they are held at thediagonal parts 4 e by the paired diagonalcorresponding parts 14. - The
retainer 5 interposed between therollers 4 usually circulates in the same circulation raceway as that of therollers 4. However, when there is space between theroller 4 and theretainer 5, theretainer 5 sometimes gets out of the normal circulation raceway. Thelip portion 15 scoops theretainer 5 out of the circulation raceway and guides it into the direction changepath 7. Theinner wall surface 15 b of thelip portion 15 is away from the raceway of the rollers and is kept out of contact with therollers 4. Therefore, therollers 4 are in contact with theedge 15 c at the loaded roller rolling path side of thelip portion 15 and theedge 15 c can be prevented from being broken. -
FIGS. 13A and 13B illustrate scooping of theroller 4 by the paired diagonal corresponding parts 14 (FIG. 13A illustrating theroller 4 that is started to be scooped andFIG. 13B illustrating theroller 4 that is being scooped). When theroller 4 moves from the loadedroller rolling path 6 to the direction changepath 7, the diagonalcorresponding parts 14 provided in theR piece 10 andend piece 11 sandwich thediagonal parts 4 e of the roller and guide it into the direction changepath 7. The width between the paired diagonalcorresponding parts 14 becomes gradually narrower as it goes deeper inside of the direction changepath 7 in such a manner that the cross section of the direction changepath 7 formed by thecontinuous path 13 and the paired diagonalcorresponding parts 14 becomes close to a rectangle gradually. Therefore, the contact surface between thediagonal part 4 e of theroller 4 and the diagonalcorresponding part 14 becomes gradually larger and theroller 4 can come into the inside of the direction changepath 7 easily. -
FIGS. 14A and 14B illustrate alip portion 15.FIG. 14A illustrates combinedR piece 10 andend piece 11, andFIG. 14B illustrates thelip portion 15 from which theend piece 11 is removed. Theinner wall surface 15 b of the lip portion is formed to be tapered in aside surface 31 a that forms a virtual trial pole ofFIG. 14B . Theinner wall surface 15 b of thelip portion 15 is tapered in such a manner that the cross sectional area of the direction changepath 7 becomes gradually larger from the direction changepath 7 to the loadedroller rolling path 6. This is to prevent therollers 4 from coming into contact with theinner wall surface 15 b of thelip portion 15. Here, if theinner wall surface 15 b of thelip portion 15 is tapered, the apex of the edge of thelip portion 15 may be sometimes displaced. -
FIG. 15 illustrates a cross section of theinner wall surface 15 b of thelip portion 15. The above-described taperedinner wall surface 15 b of thelip portion 15 is formed into V shape in such a manner that an apex angle a formed by connecting the inner walls of the paired diagonalcorresponding parts 14 and an apex 33 on thediagonal line 32 connectingdiagonal parts 4 f of theroller 4 scooped by the paired diagonalcorresponding parts 14, whichdiagonal parts 4 f are out of contact with the paired diagonal corresponding parts, is less than 90 degrees. -
FIG. 16 is a detail perspective view of the lip portion and the diagonalcorresponding parts 14. Theroller 4 is scooped up by the diagonalcorresponding parts 14 formed at the end of thecontinuous path 13. The width between the paired diagonalcorresponding parts 14 becomes narrower as they are deeper in thecontinuous path 13 and finally they are connected to each other with no space therebetween. Theretainer 5 away from the circulation raceway is scooped up into the direction changepath 7 in contact with theinner wall surface 15 b of thelip portion 15. The roller does not come into contact with theinner wall surface 15 b of thelip portion 15. The dashed line in the figure indicates the boundary between the arc part and the straight part of thecontinuous path 13. -
FIGS. 17 and 18 illustrate other examples of the circulation member to be mounted on thenut 2. Thecirculation member 3 has acirculation pipe 108 to be inserted into a through hole extending in the axial direction of thenut 2 and a pair of direction change path components to be mounted to the respective ends of thecirculation pipe 108 in the axial direction. In thecirculation member 3, an unloaded return path is formed connecting one end of the loadedroller rolling path 6 to the other. The unloaded return path has astraight path 109 extending straight in parallel with the center line of the nut 2 (seeFIG. 23 ) and a pair of curved direction change paths which are connected to the respective ends of thestraight path 109 and formed in the paired direction changepath components 112. Once eachroller 4 moves up to an end of the loadedroller rolling path 6, it is guided into the direction change path of thecirculation member 3, passes through thestraight path 109 and the opposite direction change path and is returned to the other end of the loadedroller rolling path 6. - The
circulation pipe 108 is combination of two splitpieces FIG. 18 illustrates thecirculation pipe 108 from which onesplit piece 108 b is removed. Inside thecirculation pipe 108, astraight path 109 is formed straight in parallel with the axial direction of thenut 2 . Thisstraight path 109 is twisted so that the attitude of eachroller 4 moving in thestraight path 109 can be rotated. As the attitude of the roller is rotated in thestraight path 109, it becomes possible to return theroller 4 scooped from an end of the loadedroller rolling path 6 to the other end of the loadedroller rolling path 6 with the attitudes of theroller 4 at the respective ends of the loadedroller rolling path 6 matched to each other. - The mating surfaces of the
split pieces straight path 109 of rectangular cross section. As thestraight path 109 is twisted, the apexes of the rectangle for the mating surfaces 116 are changed at a midpoint in the axial direction of thecirculation pipe 108. This is to prevent occurrence of undercut when the twistedstraight path 109 is formed in thesplit pieces circulation pipe 108 in the axial direction, a positioning hole is formed for positioning of the circulation pipe. - The direction
change path component 112 is mounted on an end surface of thenut 2.FIG. 19 illustrates a perspective view of the direction change path component. The directionchange path component 112 has combination of anR piece 110 that forms the inner peripheral side of the direction change path and anend piece 111 that forms the outer peripheral side of thedirection change path 107. - In the direction change
path component 112, a V-shaped mountain-like lip portion 114 is provided which juts toward the roller rolling surface la of V-shaped cross section of thescrew shaft 1 and scoops therollers 4 moving in the loadedroller rolling path 6 up into the direction change path. When the direction changepath component 112 is mounted on thenut 2, theedge 114 a of thelip portion 114 is placed close to the roller rolling surface la of V-shaped cross section of thescrew shaft 1. Theend 107 e of thedirection change path 107 at the opposite side to thelip portion 114 is continuous to the loadedroller rolling surface 2 a of V-shaped cross section of thenut 2. In thecontact surface 112 a of the direction changepath component 112 with thecirculation pipe 108, apositioning bore 115 is formed. As a positioning pin is inserted into the positioning bore 115 of the direction changepath component 112 and thecirculation pipe 108, they can be positioned. -
FIG. 20 is a perspective view of theR piece 110 andFIG. 21 is a perspective view of theend piece 111. Thedirection change path 107 is curved, but not twisted. The directionchange path component 112 is divided into the inner peripheralside R piece 110 and the outer peripheralside end piece 111 along the diagonal line of thedirection change path 107 of rectangular cross section. As illustrated inFIG. 20 , theR piece 110 has aflange portion 110 a for mounting on the end surface of thenut 2 and amain body portion 110 b where thedirection change path 107 is formed. In theflange portion 110 a, a mountinghole 117 is formed for mounting theR piece 110 on thenut 2. At a part of theflange portion 110 a where thedirection change path 107 is formed, a half of thelip portion 114 is formed for scooping therollers 4 moving in the loadedroller rolling path 6. TheR piece 110 may be manufactured by metal cutting or resin molding. - As illustrated in
FIG. 21 , theend piece 111 has aflange portion 111 a which is mounted on the end surface of thenut 2 and amain body portion 111 b with thedirection change path 107 formed therein. In the portion of theflange portion 111 a where thedirection change path 107 is formed, a half of thelip portion 114 for scooping up therollers 4 moving in the loadedroller rolling path 6 is formed. Theend piece 111 may be formed by cutting of metal or resin molding. - As illustrated in
FIG. 22 , theR piece 110 and theend piece 111 are superposed together a bolt (not shown) is inserted into theirflange portions nut 2 thereby to mount the direction changepath component 112 on thenut 2. When the direction changepath component 112 is mounted on the nut, thelip portion 114 is placed inside of thethread 1 c of theroller rolling surface 1 a of the screw shaft, however, it does not come into contact with the screw bottom ld of theroller rolling surface 1 a. -
FIG. 23 illustrates a structure of thedirection change path 107 seen in the axial direction of thescrew shaft 1. InFIG. 23 , theend piece 111 is removed. The chain double-dashed line in the figure indicates thecenter line 107 a of thedirection change path 107 and the broken line indicates thetangential direction 6 a of the loadedroller rolling path 6. Thedirection change path 107 has ascooping path 107 b where alip portion 114 is formed. At the connecting point which is a boundary between the loadedroller rolling path 6 and the unloaded return path, thecenter line 107 a of the scoopingpath 107 b connected to the loadedroller rolling path 6 is placed outside of thetangential direction 6 a of thecenter line 6 b of the loadedroller rolling path 6, that is, inside of thenut 2. In other words, the moving direction inside the scoopingpath 107 b of eachroller 4 moving from the loadedroller rolling path 6 to thescooping path 107 b is directed to the outside of the tangential direction of the loadedroller rolling path 6. Then, in order to connect thescooping path 107 b to thestraight path 109, thedirection change path 107 is curved into an arc at a midpoint to thestraight line 109 and is connected to the end of thestraight path 109. After thecenter line 107 a of thedirection change path 107 is designed as described above, theroller 4 is moved along thecenter line 107 thereby to be able to design thedirection change path 107. Here, thecenter line 10 of thedirection change path 107 seen in the side surface direction of thescrew shaft 1 is direction in the lead direction of thescrew shaft 1. - As the moving direction of each
roller 4 inside the scoopingportion 107 b is directed outside of thetangential direction 6 a, theedge 114 a of thelip portion 114 can be extended toward the loadedroller rolling path 6 while the enough thickness of thelip portion 114 is assured. With this structure, the unconstrained area of theroller 4 from the loadedroller rolling path 6 into thelip portion 114 is shortened and it becomes possible to prevent skewing of theroller 4 in the unconstrained area. -
FIG. 24 illustrates the raceway of eachroller 4 scooped up by thelip portion 114. In the loadedroller rolling path 6, theroller 4 rolls in line contact with the two points of the roller rolling surface la of thescrew shaft 1 and the loadedroller rolling surface 2 a of thenut 2. Once theroller 4 is moved up to an end of the loadedroller rolling path 6, it enters thelip portion 114. There, just before theroller 4 gets out of the loadedroller rolling path 6, its end in the moving direction enters thelip portion 114. To be exact, as illustrated inFIG. 25 , when thecenter 4 d of theroller 4 is positioned at the transition point from the loadedroller rolling path 6 to the unloaded return path, theedge 114 of thelip portion 114 covers the end of theroller 4 in the moving direction. In other words, the distance L1 from theboundary 120 between the loaded roller rolling path and the unloaded return path to the lip portion 114 (seeFIG. 25 ) is smaller than the radius of theroller 4. The angle α1 of thecenter line 107 a of the scoopingpath 107 b relative to thetangential direction 6 a (seeFIG. 23 ) is set to such an angle that theedge 114 a of thelip portion 114 covers the end of theroller 4 in the moving direction. - As illustrated in
FIG. 25 , theroller 4 enters thelip portion 114 while it keeps the attitude inside the loadedroller rolling path 6. Therefore, it is possible to prevent skewing of theroller 4 moving from the loadedroller rolling path 6 to thelip portion 114. When theroller 4 enters thelip portion 114, theedge 114 a of thelip portion 114 is out of contact with theroller 4. Therefore, it is possible to prevent damage to theedge 114 a of thelip portion 114. When theroller 4 further comes into thelip portion 114, the inner wall surface of thelip portion 114 comes into contact with the side surface of theroller 4 and it guides theroller 4 into thedirection change path 107. -
FIGS. 26 and 27 illustrate thedirection change path 107 formed in theR piece 110 and theend piece 111. Thedirection change path 107 of theR piece 110 and theend piece 111 has the scoopingportion 107 b directed outside of thetangential direction 6 a of the loadedroller rolling path 6, a bentintermediate path 107 c and acommunication path 107 d connecting theintermediate path 107 c to thestraight path 109. -
FIGS. 28A and 28B are side views of aroller roller 4 inFIG. 28A has spherical end surfaces and theroller 121 inFIG. 28B has circularly chamfered end surfaces 121 a. When theroller 121 with chamfered end surfaces is used to circulate, it is constrained at theedge 114 a of thelip portion 114 more securely. This reveals that theroller 4 can move smoothly when it has spherical end surfaces. In addition, when theend surface 4 a of theroller 4 is spherical, the curvature radius of theend surface 4 a becomes larger than that of the circularly-chamferedroller 4. Inclination of thetangential direction 4 f of theend surface 4 a at the elevation change can be smaller than theinclination 121 e of theroller 121 also when the roller moves on the elevation change between the components. Hence, theroller 4 is prevented from being caught in the elevation difference. Here, when theend surface 4 a of the roller is spherical, theroller 4 becomes easy to be inclined and therefore, it is preferable that the retainer is interposed betweenadjacent rollers 4 to prevent skewing. -
FIG. 29 illustrates another example of thelip portion 114. Thelip portion 114 forms a mountain by combining afirst wall part 126 b and asecond wall part 126 a at the apex 126 c. Thefirst wall part 126 b is positioned to the end surface side of the roller and thesecond wall part 126 a is positioned to the side surface side of theroller 4. Thefirst wall part 126 b is cut short. Theedge 128 b of thefirst wall part 126 b is shifted from theedge 128 a of thesecond wall part 126 a, which starts at the apex 126 c, and theedge 128 b is away from the loadedroller rolling path 6 more than theedge 128 a of thesecond wall part 126 a. Thus, as the length of thelip portion 114 is differentiated between the end surface side and side surface side of theroller 4, it becomes possible to constrain first the side surface of theroller 4 and then the end surface of theroller 4. When the end surface of theroller 4 abuts against thelip portion 114, thelip portion 114 may be damaged. As the side surface of theroller 4 is first constrained and then, after the angle of the end surface of theroller 4 is maintained constant the end surface of theroller 4 is constrained thereby to prevent damage to thelip portion 114. - The present invention is not limited to the above-mentioned exemplary embodiments and may be embodied in various forms without departing from the scope of the invention. For example, the continuous path of the direction change path component may extend directed outside not of the tangential direction of the loaded roller rolling path of the nut, but of tangential direction seen in the axial direction of the nut. With this structure, the paired diagonal corresponding parts can hold the diagonal parts of the rollers more stably and also the rollers that have just got out of the loaded roller rolling path.
- The circulation member is not limited to such an endcap type circulation member as in the embodiments and may be a return pipe formed by bending both ends of a pipe. Besides, the rollers may be parallel-arranged with axis lines of the adjacent rollers kept in parallel with each other, or may be cross-arranged with the axis lines orthogonal to each other. Each roller used may be a tapered roller having tapered side surfaces instead of a cylindrical roller. Further, the axis lines of plural rollers parallel-arranged in the respective two roller rolling surfaces may be directed in the same direction. Furthermore, for example, the scooping portion may not be the lip portion jutting to the screw shaft side as described above but a boat-bottom shaped scooping portion for scooping the parts on the diagonal line of the roller as a boat-bottom scooping of a ball screw.
- The present application is based on Japanese Patent Application Nos. 2007-286791 filed on Nov. 2, 2007 and 2007-286792 filed on Nov. 2, 2007, and their contents are incorporated by reference herein.
Claims (12)
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2007286791A JP4587406B2 (en) | 2007-11-02 | 2007-11-02 | Roller screw and roller circulation method of roller screw |
JP2007-286791 | 2007-11-02 | ||
JP2007286792A JP4587407B2 (en) | 2007-11-02 | 2007-11-02 | Roller screw and roller circulation method of roller screw |
JP2007-286792 | 2007-11-02 | ||
PCT/JP2008/069633 WO2009057630A1 (en) | 2007-11-02 | 2008-10-29 | Roller screw |
Publications (2)
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US20100263467A1 true US20100263467A1 (en) | 2010-10-21 |
US8336415B2 US8336415B2 (en) | 2012-12-25 |
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US12/740,924 Active 2029-04-19 US8336415B2 (en) | 2007-11-02 | 2008-10-29 | Roller screw |
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US (1) | US8336415B2 (en) |
CN (1) | CN101903686B (en) |
DE (1) | DE112008002939B4 (en) |
TW (1) | TWI437173B (en) |
WO (1) | WO2009057630A1 (en) |
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US20080245170A1 (en) * | 2004-09-08 | 2008-10-09 | Thk Co., Ltd. | Roller Screw |
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JP5527028B2 (en) * | 2010-06-07 | 2014-06-18 | 株式会社ジェイテクト | Ball screw device and electric power steering device |
TW201335515A (en) * | 2012-02-16 | 2013-09-01 | Chiuan Yan Technology Co Ltd | Roller retention frame |
JP1524390S (en) * | 2014-07-10 | 2015-05-25 | ||
JP1524391S (en) * | 2014-07-10 | 2015-05-25 | ||
USD755619S1 (en) * | 2015-01-30 | 2016-05-10 | Kuroda Precision Industries Ltd. | Ball screw |
JP6980349B2 (en) * | 2018-01-22 | 2021-12-15 | Thk株式会社 | Ball screw device |
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CN101903686B (en) | 2013-05-29 |
WO2009057630A1 (en) | 2009-05-07 |
TWI437173B (en) | 2014-05-11 |
CN101903686A (en) | 2010-12-01 |
TW200936912A (en) | 2009-09-01 |
DE112008002939B4 (en) | 2023-10-12 |
US8336415B2 (en) | 2012-12-25 |
DE112008002939T5 (en) | 2010-11-25 |
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